Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture Slides prepared by Vince Austin, University of Kentucky 16 The Endocrine System Part B

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Major Endocrine Organs Figure 16.1

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Pituitary gland – two-lobed organ that secretes nine major hormones  Neurohypophysis – posterior lobe (neural tissue) and the infundibulum  Receives, stores, and releases hormones from the hypothalamus  Adenohypophysis – anterior lobe, made up of glandular tissue  Synthesizes and secretes a number of hormones Major Endocrine Organs: Pituitary (Hypophysis)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The posterior lobe is a down growth of hypothalamic neural tissue  Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract)  Hormones are transported from the hypothalamus to the posterior pituitary for storage.  The posterior lobe is not a true gland as it does not have glandular tissue, it is only used for storage an communication. Pituitary-Hypothalamic Relationships: Posterior Lobe

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Anterior Pituitary (Adenohypophysis)  The anterior pituitary is a true gland.  It manufactures and releases a variety of hormones.  Used to be called the “master gland”.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The six hormones of the adenohypophysis:  Are abbreviated as GH, TSH, ACTH, FSH, LH, and PRL  Regulate the activity of other endocrine glands  In addition, pro-opiomelanocortin (POMC):  Is enzymatically split into other hormones, including a type of endorphin and melanin stimulating hormone. Adenophypophyseal Hormones

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 16.5 Major Endocrine Organs: Pituitary (Hypophysis)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The largest endocrine gland, located in the anterior neck, consists of two lateral lobes connected by a median tissue mass called the isthmus  Composed of follicles that produce the glycoprotein thyroglobulin  Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone  Other endocrine cells, the parafollicular cells, produce the hormone calcitonin Thyroid Gland

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 16.7 Thyroid Gland

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Thyroid hormone – the body’s major metabolic hormone  Consists of two closely related iodine-containing compounds  T 4 – thyroxine; has two tyrosine molecules plus four bound iodine atoms  T 3 – triiodothyronine; has two tyrosines with three bound iodine atoms Thyroid Hormone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  TH is concerned with:  Glucose oxidation  Increasing metabolic rate  Heat production  TH plays a role in:  Maintaining blood pressure  Regulating tissue growth  Developing skeletal and nervous systems  Maturation and reproductive capabilities Effects of Thyroid Hormone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Parathyroid Glands  Tiny glands embedded in the posterior aspect of the thyroid  Cells are arranged in cords containing oxyphil and chief cells  Chief (principal) cells secrete PTH  PTH (parathormone) regulates calcium balance in the blood

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Parathyroid Glands Figure 16.10a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Adrenal glands – paired, pyramid-shaped organs atop the kidneys  Structurally and functionally, they are two glands in one  Adrenal medulla – nervous tissue that acts as part of the SNS  Adrenal cortex – glandular tissue derived from embryonic mesoderm Adrenal (Suprarenal) Glands

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 16.12a Adrenal Cortex

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Synthesizes and releases steroid hormones called corticosteroids  Different corticosteroids are produced in each of the three layers  Zona glomerulosa – mineralocorticoids (chiefly aldosterone)  Zona fasciculata – glucocorticoids (chiefly cortisol)  Zona reticularis – gonadocorticoids (chiefly androgens) Adrenal Cortex

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Regulate the electrolyte concentrations of extracellular fluids  Aldosterone – most important mineralocorticoid  Maintains Na + balance by reducing excretion of sodium from the body  Stimulates reabsorption of Na + by the kidneys Mineralocorticoids

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Help the body resist stress by:  Keeping blood sugar levels relatively constant  Maintaining blood volume and preventing water shift into tissue  Cortisol provokes:  Gluconeogenesis (formation of glucose from noncarbohydrates)  Rises in blood glucose, fatty acids, and amino acids Glucocorticoids (Cortisol)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Most gonadocorticoids secreted are androgens (male sex hormones), and the most important one is testosterone  Androgens contribute to:  The onset of puberty  The appearance of secondary sex characteristics  Sex drive in females  Androgens can be converted into estrogens after menopause Gonadocorticoids (Sex Hormones)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Made up of chromaffin cells that secrete epinephrine and norepinephrine  Epinephrine is the more potent stimulator of the heart and metabolic activities  Norepinephrine is more influential on peripheral vasoconstriction and blood pressure Adrenal Medulla InterActive Physiology ® : Endocrine System: Response to Stress PLAY

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Stress and the Adrenal Gland

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  A triangular gland, which has both exocrine and endocrine cells, located behind the stomach  Acinar cells produce an enzyme-rich juice used for digestion (exocrine product)  Pancreatic islets (islets of Langerhans) produce hormones (endocrine products)  The islets contain two major cell types:  Alpha (  ) cells that produce glucagon  Beta (  ) cells that produce insulin Pancreas

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose Levels  The hyperglycemic effects of glucagon and the hypoglycemic effects of insulin Figure 16.17

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  A 29-amino-acid polypeptide hormone that is a potent hyperglycemic agent  Its major target is the liver, where it promotes:  Glycogenolysis – the breakdown of glycogen to glucose  Gluconeogenesis – synthesis of glucose from lactic acid and noncarbohydrates  Release of glucose to the blood from liver cells Glucagon

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  A 51-amino-acid protein consisting of two amino acid chains linked by disulfide bonds  Insulin:  Lowers blood glucose levels  Enhances transport of glucose into body cells  Counters metabolic activity that would enhance blood glucose levels Insulin

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Paired ovaries in the abdominopelvic cavity produce estrogens and progesterone  They are responsible for:  Maturation of the reproductive organs  Appearance of secondary sexual characteristics  Breast development and cyclic changes in the uterine mucosa Gonads: Female

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Testes located in an extra-abdominal sac (scrotum) produce testosterone  Testosterone:  Initiates maturation of male reproductive organs  Causes appearance of secondary sexual characteristics and sex drive  Is necessary for sperm production  Maintains sex organs in their functional state Gonads: Male

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Small gland hanging from the roof of the third ventricle of the brain  Secretory product is melatonin  Melatonin is involved with:  Day/night cycles  Physiological processes that show rhythmic variations (body temperature, sleep, appetite) Pineal Gland

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pineal Gland

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Lobulated gland located deep to the sternum in the thorax  Major hormonal products are thymopoietins and thymosins  These hormones are essential for the development of the T lymphocytes (T cells) of the immune system Thymus

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Thymus Gland

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Heart – produces atrial natriuretic peptide (ANP), which reduces blood pressure, blood volume, and blood sodium concentration  Gastrointestinal tract – enteroendocrine cells release local-acting digestive hormones  Placenta – releases hormones that influence the course of pregnancy Other Hormone-Producing Structures

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Kidneys – secrete erythropoietin, which signals the production of red blood cells  Skin – produces cholecalciferol, the precursor of vitamin D  Adipose tissue – releases leptin, which is involved in the sensation of satiety, and stimulates increased energy expenditure Other Hormone-Producing Structures